All of lore.kernel.org
 help / color / mirror / Atom feed
From: Petr Mladek <pmladek@suse.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: David Laight <David.Laight@ACULAB.COM>,
	'Steven Rostedt' <rostedt@goodmis.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Dmitriy Vyukov <dvyukov@google.com>,
	Alexander Potapenko <glider@google.com>,
	Fengguang Wu <fengguang.wu@intel.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages.
Date: Fri, 30 Nov 2018 17:01:47 +0100	[thread overview]
Message-ID: <20181130160147.r6idgsr2biy5rwap@pathway.suse.cz> (raw)
In-Reply-To: <1d29f61a-8f36-ab1c-bb92-402ee9ad161d@i-love.sakura.ne.jp>

On Thu 2018-11-29 19:09:26, Tetsuo Handa wrote:
> On 2018/11/28 22:29, David Laight wrote:
> > I also spent a week trying to work out why a customer kernel was
> > locking up - only to finally find out that the distro they were
> > using set 'panic on opps' - making it almost impossible to find
> > out what was happening.

Did the machine rebooted before the messages reached console or
did it produced crash-dump or frozen?

panic() tries relatively hard to flush the messages to the console,
see printk_safe_flush_on_panic() and console_flush_on_panic().
It is less aggressive when crashdump is called. It might deadlock
in console drivers.

Hmm, it might also fail when another CPU is still running and
steals console_lock. We might want to disable
console_trylock_spinning() if the caller is not
panic_cpu.


> On 2018/11/26 13:34, Sergey Senozhatsky wrote:
> > Or... Instead.
> > We can just leave pr_cont() alone for now. And make it possible to
> > reconstruct messages - IOW, inject some info to printk messages. We
> > do this at Samsung (inject CPU number at the beginning of every
> > message. `cat serial.0 | grep "\[1\]"` to grep for all messages from
> > CPU1). Probably this would be the simplest thing.
> 
> Yes, I sent a patch which helps reconstructing messages at
> http://lkml.kernel.org/r/1543045075-3008-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp .

All the buffering approaches have problems that cannot be solved
easily. The prefix-based approach looks like the best alternative
at the moment.

Best Regards,
Petr

  reply	other threads:[~2018-11-30 16:01 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-02 13:31 [PATCH v6 1/3] printk: Add line-buffered printk() API Tetsuo Handa
2018-11-02 13:31 ` [PATCH 2/3] mm: Use line-buffered printk() for show_free_areas() Tetsuo Handa
2018-11-07 14:07   ` Petr Mladek
2018-11-02 13:31 ` [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages Tetsuo Handa
2018-11-02 13:36   ` Peter Zijlstra
2018-11-03  2:00     ` Tetsuo Handa
2018-11-06  8:38     ` Petr Mladek
2018-11-06  9:05       ` Sergey Senozhatsky
2018-11-06 12:57         ` Petr Mladek
2018-11-06  9:56       ` Tetsuo Handa
2018-11-07 15:19   ` Petr Mladek
2018-11-08  4:45     ` Sergey Senozhatsky
2018-11-08 11:37       ` Tetsuo Handa
2018-11-09  6:12         ` Sergey Senozhatsky
2018-11-09  9:55           ` Tetsuo Handa
2018-11-09 15:43             ` Petr Mladek
2018-11-10  2:42               ` Tetsuo Handa
2018-11-23 12:46                 ` Petr Mladek
2018-11-23 13:12                   ` Tetsuo Handa
2018-11-23 15:56                   ` Steven Rostedt
2018-11-24  0:24                     ` Tetsuo Handa
2018-11-26  4:34                       ` Sergey Senozhatsky
2018-11-28 13:29                     ` David Laight
2018-11-29 10:09                       ` Tetsuo Handa
2018-11-30 16:01                         ` Petr Mladek [this message]
2018-11-10  8:52               ` Tetsuo Handa
2018-11-23 12:52                 ` Petr Mladek
2018-11-09 14:08           ` Linus Torvalds
2018-11-09 14:42             ` Steven Rostedt
2018-11-08 11:53       ` Petr Mladek
2018-11-08 12:44         ` Sergey Senozhatsky
2018-11-08 14:21           ` Sergey Senozhatsky
2018-11-09  9:54     ` Tetsuo Handa
2018-11-02 14:40 ` [PATCH v6 1/3] printk: Add line-buffered printk() API Matthew Wilcox
2018-11-03  1:55   ` Tetsuo Handa
2018-11-02 18:12 ` kbuild test robot
2018-11-02 18:12   ` kbuild test robot
2018-11-06 14:35 ` Sergey Senozhatsky
2018-11-07 10:21   ` Petr Mladek
2018-11-07 12:54     ` Tetsuo Handa
2018-11-08  2:21     ` Sergey Senozhatsky
2018-11-08 11:24       ` Petr Mladek
2018-11-08 11:46         ` Tetsuo Handa
2018-11-08 12:30         ` Sergey Senozhatsky
2018-11-09 14:10           ` Petr Mladek
2018-11-12  7:59             ` Sergey Senozhatsky
2018-11-12 10:42               ` Tetsuo Handa
2018-11-17 10:14               ` Tetsuo Handa
2018-11-07 10:52   ` Tetsuo Handa
2018-11-07 11:01     ` David Laight
2018-11-07 12:00       ` Petr Mladek
2018-11-07 11:45     ` Petr Mladek
2018-11-08  2:30     ` Sergey Senozhatsky
2018-11-07 13:41 ` Petr Mladek
2018-11-07 14:06 ` Petr Mladek

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181130160147.r6idgsr2biy5rwap@pathway.suse.cz \
    --to=pmladek@suse.com \
    --cc=David.Laight@ACULAB.COM \
    --cc=akpm@linux-foundation.org \
    --cc=dvyukov@google.com \
    --cc=fengguang.wu@intel.com \
    --cc=glider@google.com \
    --cc=jpoimboe@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mingo@redhat.com \
    --cc=penguin-kernel@i-love.sakura.ne.jp \
    --cc=peterz@infradead.org \
    --cc=rostedt@goodmis.org \
    --cc=sergey.senozhatsky.work@gmail.com \
    --cc=sergey.senozhatsky@gmail.com \
    --cc=torvalds@linux-foundation.org \
    --cc=will.deacon@arm.com \
    --subject='Re: [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages.' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.